Yumi has been married for three months to a man with a child from a previous marriage. Although her relationship with her husband is good, her relationship with her son, Kazuki, has not been going well. So her husband suggests they go on a trip to a hot spring, and the two of them begin to grow closer. However, Kazuki, who senses Yumi as a woman, is unable to suppress his rising desire and attacks her while she is asleep... Yumi is made to climax many times by his intense and earnest thrusts, and she writhes in agony. Their sex is a perfect match that she could never experience with her husband, and before she knows it, her body can no longer resist his cock...